Sometimes historical changes march onstage to the sound of trumpet fanfares. And sometimes they arrive with what seems remarkably little notice by a distracted audience. Such, at least, were my own feelings last spring when the Senate voted 80—19 to approve the admission to the North Atlantic Treaty Organization of Poland, Hungary, and the Czech Republic. How could NATO, a defensive anti-Communist coalition of 1949, come to embrace three former Soviet satellites and presumptive U.S. enemies almost ten years after the simultaneous end of the Cold War and the U.S.S.R.?

It’s not that there were no counterarguments at all. Plenty of editorial columnists declared that the move was provocative and unnecessary, but these views persuaded only nineteen senators out of a hundred, and the issue got relatively little headline play. My personal recollection was that more sound and fury had surrounded the original creation of NATO almost half a century ago, more awareness that the United States was taking a giant step away from a powerful tradition of “no entangling alliances” and crossing a historic divide.

And so it was. Overall, the 1940s were more intense times. Yet the record held a surprise. The actual Senate vote of 1949 to join in creating NATO was as lopsided as this year’s to move its shield eastward again. It was 82-13 in a Senate with four fewer members. Part of that success for our State Department was due to the atmosphere of the day; part, to skillful advocacy. But another factor was a certain cultivated ambiguity in the exact meaning of the treaty. Defenders of the current expansion of NATO say that it’s an open-ended association of “free” nations, with missions that can evolve beyond its clearly understood 1949 purpose of “containing” the Soviet Union under Stalin. Are they right? What do the facts show about the “original intent” of NATO’s founders?

There’s little doubt it was primarily to fight the Cold War. The alliance between the U.S.S.R. and the West had been crumbling all through 1946, mainly in fights over resuscitating occupied Germany’s economy. March of 1947 brought U.S. financial aid to Greece and Turkey via the Truman Doctrine of helping “free peoples” resist Communist pressure. June saw the proposal of the Marshall Plan, likewise promoted as a measure to strengthen non-Communist nations. Then, near the end of the year, the British foreign secretary, Ernest Bevin, wrote to Secretary of State George Marshall, “I am convinced that the Soviet Union will not deal with the West on any reasonable terms in the foreseeable future.” Bevin therefore proposed a Western European “union . . . backed by the United States and the Dominions,” whose nucleus might be a defensive alliance to be known as the Brussels Pact that Bevin was trying to form among Britain, France, Belgium, the Netherlands, and Luxembourg.

Marshall liked the idea but could hardly guarantee American backing. Nineteen forty-eight would be an election year in a nation in no mood for possible new overseas commitments. And then there was the Senate. It was, in the first place, eager to regain its constitutional role in foreign policymaking after years of wartime subordination to the Chief Executive. In the second place, it was Republican. Although the United States had already joined the United Nations, any treaty binding it further to collective security might well meet the fate that a Republican Senate had dished out to Woodrow Wilson in 1919. Moreover, one of isolationism’s strongest voices, Ohio’s Sen. Robert Taft, was a dominant Republican leader.

Luckily for Secretary Marshall, however, there was a split in the opposition ranks. The chairman of the Senate Foreign Relations Committee was Michigan’s Arthur Vandenberg, a cigar-smoking well-liked Senate insider converted from Midwestern isolationism to internationalism in 1945. The other card in Marshall’s hand was the force of anti-Communism in neutralizing isolationism, and in a swift and exciting sequence of events, Moscow dealt him a few more, all aces.

Soviet diplomats had already taken a firm stand against any Allied measures to help ruined Germany. Then, in February of 1948, Communists engineered a coup in Czechoslovakia that turned it into a Soviet puppet state. Were these signs of a Soviet drive to control Central Europe—and perhaps more? The West thought yes, and a sense of being on the brink of war swept Washington. On St. Patrick’s Day, 1948, Truman, specifically naming the Soviet Union as a threat, asked Congress for a military buildup and renewal of the draft. The Brussels Pact was completed on the same date, and the National Security Council soon recommended that the United States enter into formal agreement with the Brussels Pact nations—plus the Scandinavian countries and Italy—to regard an attack on any one of them as an attack on all. Britain, France, and the United States unveiled plans to issue new, sounder German currency in their occupation zones, and the Russians countered with harassing moves that would culminate in the Berlin blockade.

Who could have guessed we’d ever plan joint maneuvers with Czech, Polish, and Hungarian colleagues?

On Capitol Hill Senator Vandenberg said it was important to act, but “why,” he asked, “should a Democratic President get all the kudos in an election year?” He introduced a resolution that urged the President to seek “progressive development of . . . collective [arrangements] for self-defense” plus the “association of the U.S. by constitutional process with such arrangements.” In a crisis atmosphere, only twelve days before the Russians shut off land access to Berlin, the Vandenberg Resolution was overwhelmingly adopted on June 11.

The resolution put the Senate at least provisionally on board and gave the State Department a yellow light to proceed—yellow until after the November elections, when Truman’s triumph turned it to green. In February 1949 there was a change of cast: a new and elegant Secretary of State, Dean Acheson (Marshall had retired), and a new chairman of the Senate Foreign Relations Committee, Texan Tom Connally, a loyal Democrat. Acheson and Undersecretary Robert Lovett began informal, shirtsleeved talks in Washington with ambassadors from the Brussels Pact nations and Canada. Their goal: a treaty written in such plain language, said one U.S. draftsman, that “a milkman in Omaha [could] understand it"—and presumably be willing to send his son to fight under its provisions.

But clarity and compromise are sometimes at odds, and here is where ambiguity about NATO’s essence began. Even in 1949 not all the nations invited to join were “Atlantic” or “free.” Italy, thought to be vulnerable to Communist penetration, was brought into the fold to tie it more tightly to the West, a move that disgruntled its left-out Mediterranean neighbors Greece and Turkey, which had a more urgent claim to protection. Portugal, under the authoritarian rule of Antonio Salazar, was invited, but not Franco’s anti-Communist and Atlantic-facing Spain. To be sure, Spain had given aid and comfort to the Axis, but Italy was actually a former enemy.

The Senate still posed problems. While the Europeans wanted language that unmistakably bound the United States to fight, senators were not ready to relinquish their war-making powers. So Article 5 of the treaty, as drafted, bound each member to assist any one of them attacked “by taking forthwith . . . such action as it deems necessary, including the use of armed force. . . .” Including did not mean “mandated.”

This wiggle room for the Senate was enlarged by broadening the exclusively military (and anti-Soviet) nature of the treaty. Article 2 said that the signatories would contribute to “peaceful and friendly international relations” and “encourage economic collaboration” among themselves. And Article 10 said that by unanimous agreement the members could invite in “any other European State in a position to further the principles of this Treaty” and “contribute to the security of the North Atlantic area.”

These elastic provisions (like some in the U.S. Constitution) arguably leave a door ajar for many reinterpretations, but they may also account for the fact that NATO will soon celebrate a half-century birthday despite many changes in the world picture. Perhaps some foresighted senators who voted to ratify the treaty on July 21, 1949, could anticipate the admission of Greece and Turkey (1952), of a re-armed West Germany (1955), and even, finally, of Spain (1982). But who among them would have guessed that America’s next three wars would be in Asia and the Middle East and that none of them would be formally declared by Congress—much less that a day might come, as is now likely, when U.S. generals would sit down to plan joint maneuvers with Czech, Polish, and Hungarian colleagues? We are controlled by unanticipated events far more than we like to think. Dean Acheson himself, with a lively sense of the ironies of history, noted in his memoirs that on the April day of formally signing the treaty he had worked so hard for, President Truman expressed his conviction that had it existed in 1914 or 1939 it “would have prevented the acts . . . which led to two world wars.” Among the selections played by the Marine Band for the occasion, however, were two Gershwin numbers: “I’ve Got Plenty of Nothin’” and “It Ain’t Necessarily So.”